Preparation of alginate–quaternary ammonium complex beads and evaluation of their antimicrobial activity

Alginate–quaternary ammonium complex beads with antimicrobial activity were prepared by the reaction of sodium alginate (SA) with 3-(trimethoxysilyl)propyl-octadecyldimethylammonium chloride (TSA) in acid solution, followed by crosslinking with CaCl2. FTIR spectroscopy analysis showed that the resulting complex was formed mainly through covalent bonds between the hydroxyl groups of SA and the methoxysilyl groups of TSA. The complex beads exhibited a maximum swelling of 20% in water at 37 °C and were not hydrolyzed in water during experiments lasting for 30 days. The in vitro antimicrobial activity of the complex beads was evaluated against four species of bacteria and fungi. The test microorganisms were completely eliminated within 20 min when treated with 5% (v/v) complex beads, which showed a wide spectrum of excellent antimicrobial activity. The antimicrobial activity of the complex beads was retained after 10 cycles of washing and drying. The present results indicate that these SA–TSA complex beads are a new type of insoluble cationic polymer that can kill or remove microorganisms in water by mere contact without releasing the reactive agent.